Questions tagged [8085]

An eight bit microprocessor made by Intel in 1976.

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2answers
38 views

how to write a 8085 assembly language to sort 5 data bytes in ascending order [on hold]

Needed advise on how to program using 8085 simulator. tried many ways but could not get the answer
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1answer
47 views

How do I produce WE in this diagram?

I have designed a memory system that has 10KB ROM followed by 6KB of RAM. The ROM begins at 0000H. I had to use two 4K x 8bit ROMs and one 2K x 8 bit ROM. I also have to use one 2K x 8bit RAM and a 4K ...
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1answer
61 views

Is a multiplexer needed to read from memory

we need to enable a register to write into that register, which is done using a decoder. even if we enable 1 register using decoder, given that RD(bar) is 0, all registers can still produce an output. ...
0
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1answer
65 views

Microprocessor 8085 regains control of the bus

a) immediately after HOLD goes Low b) immediately after HOLD goes high c) after half clock cycle has passed once HLDS goes low d) after half clock cycle after HLDA goes high This question was asked ...
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1answer
79 views

Building a simple manual Intel 8085 study kit

I am toying with the idea of building an Intel 8085 demonstration/study kit which would consist of an Intel 8085 microprocessor on a PCB, where all input nodes (including the clock X1, X2) would be ...
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1answer
272 views

Why RST instructions are called one byte call instruction in 8085 [closed]

Why RST instructions are called one byte call instruction in 8085 ?
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1answer
222 views

Parity flag in 8085 microprocessor

What happens to the parity flag of an Intel 8085 microprocessor when there is no '1' bit in the accumulator? For example, if the following instruction executes, MVI A, 05H MVI B, 05H SUB B the ...
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1answer
2k views

What is increment/decrement address latch in 8085

Can you please explain about increment/decrement latch in 8085. I am currently studying registers and encountered this in the array of register section. Here are the things i found when i googled and ...
2
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1answer
87 views

IO mapped IO design problem

While going through the solution of the above problem i noticed something like below. Address of port A becomes 11100000. Can't get that. I am confused why it's not 01100000. Thank you!!
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1answer
113 views

What is the best way to implement spi using 8085? [closed]

I have to make a compass using 8085. I have to take serial data from magnetometer of mpu9250. Should i prefer bit banging to implement spi or make parallel out and parallel in hardware using shift ...
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2answers
2k views

Why don't we have an instruction called LDAX H in 8085 microprocessor?

Whereas we have instructions such as LDAX B , LDAX D !!!
2
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2answers
71 views

microproccessor 8085

What is the need of enabling 8 bit register in memory using address bus to read data from it?Enabling is required to write data into register and after that to read can't we just provide read signal ...
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1answer
153 views

8085 Programming Basics

Bcz of CALL, SP will be decremented by 2. Then bcz of POP, SP will get incremented by 2. So, SP will be 27FFH. But, I am confused with HL register part. Please help me with the above problem.
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2answers
112 views

Why is there no tri-state during T2 state of this machine cycle?

My teacher provided this as part of printed notes where he writes there is no tristate during the T2 state of Memory Write Cycle. I am quite confused about why it is so. After a short search in the ...
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1answer
1k views

8085 - binary equivalent of MOV and it's corresponding timing diagram

I've got two questions here: #1 The MOV A,B is said to be a one byte instruction, where B = 000 and A = 111, then MOV should be equal to 00, but, The binary representation of the BC Rp is 00. So, I'...
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1answer
155 views

How to save carry bits in 8085?

Suppose two 16bits numbers are added in 8085, then there is a carry, so, how do I save the carry into a memory location?
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1answer
564 views

8085 programming the ani instruction

Why is the AC flag set while using the ANI instruction in 8085: MVI A, A3H ANI 97H HLT The sign flag is set which is ...
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2answers
6k views

In microprocessor 8085, how can I clear/reset all flags(s,z,ac,p,cy) without affecting contents of accumulator? [duplicate]

I only know the code in which accumulator contents are affected. It is not a duplicate as I have asked for a solution which doesn't affect accumulator.
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1answer
250 views

Why the address of 8085 interrupt are 8 locations apart and not in continuation

If it's for Interrupt Service Routine (ISR) in which microprocessor pushes the content of program Counter(PC) to stack and then loads the Vector address in PC and starts executing the ISR stored in ...
2
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2answers
3k views

What exactly is latch?

I've very less knowledge in electronics, I've read that a latch is a simple circuit that stores 1 bit of data (or state). A Latch is a circuit that has two stable states and can be used to store ...
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3answers
1k views

Overflow results into wrong sign-flag bit set in 8085 microprocessor .

In case of 8085 microprocessor when the MSB bit of accumulator is 1 then sign flag becomes 1 ( simply copy the result's msb) , my question is that : When we add two positive numbers say 44H(01000100) ...
0
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1answer
264 views

HOLD signal in 8085

What happens to an 8085 system if a square wave signal of 1KHz frequency is applied to the HOLD signal of 8085? The frequency of operation is 2MHz. Therefore, if the every 0.5ms, the HOLD pin goes ...
0
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0answers
539 views

Pending interrupts in 8085

I've gotten a little confused with what the definition of the pending interrupt is. That is when will this bit be set to 1 and read by using the RIM instruction. My confusion is that: When an ...
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3answers
1k views

does 8085 CPU have an extra register within ALU?

From the 8085 CPU architecture, when ALU done calculation, the result is clocked back to accumulator A on next clock edge. But accumulator A is directly wired as ALU input, what if the clock edge didn'...
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1answer
191 views

Slow clock for 8085

I want to find out if my purchased 8085 works. I'm thinking of: pulling down the data bus and interrupt lines (equivalent to NOPs) using a slow RC clock (1 Hz or so) drive LEDs through BJTs with the ...
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3answers
822 views

Invalid opcodes

What happens when a microprocessor like the 8085 fetches an invalid opcode, i.e. not part of its instruction set, from memory and attempts to decode and run it? I found, in some forum, that invalid ...
3
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2answers
1k views

Building an Intel 8085 trainer

I'd like to build an Intel 8085 trainer for a final year project. The trainer will be used by students and will basically accept machine code entered by students, load these into RAM and run the code. ...
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2answers
8k views

How to determine no of bytes of an instruction of 8085 microprocessor?

Is there any logical way to understand no of bytes corresponding to an instruction in 8085 microprocessor? e.g: MOV A,M is a one byte instruction, but how, I don't understand. Or do I have to ...
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5answers
333 views

Does an ALU always do add and sub, but only returns one of the results?

Pretty simple question. Does an ALU internally always do multiple operations like add, sub, div, mul, ... and you simply have to specify which result you want to return? I was told that it does that, ...
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1answer
984 views

Address Decoding in 8085

RAM (8KB, requires 13 bits A0-A12) Start: 0110 0000 0101 0000 (6050h) End: 1000 0000 0100 1111 (804Fh) ROM1 (8KB, requires 13 bits A0-A12) Start: 1000 0000 0101 0000 (8050h) End: 1010 0000 0100 ...
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2answers
353 views

Interrupt in 8085 microprocessor

What's the mechanism whereby the external device places a RST instruction on the bus, along with an interrupt # 0-7? I only know that external device sends signal to INTR pin to interrupt 8085
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1answer
310 views

What is the triggering level of INTR interrupt? [closed]

In the book we are told about the triggering level of other interrupts but I could not found any statements about the triggering level of INTR.please answer.
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1answer
2k views

How to reset all flags in 8085 without an arithmetic or logic operation?

How can I reset all flags in 8085 without an arithmetic or logic operation?
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1answer
666 views

In 8085, what is peripheral mapped I/O?

Is the peripheral mapped I/O different from what is known as port-mapped I/O or simply known as I/O mapped I/O? I don't see the usage of the term "peripheral mapped I/O" around much. Was it only ...
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1answer
960 views

How to set flags in microprocessor 8085 after IN instruction?

When microprocessor reads an input port, the instruction IN does not set any flag. If the input reading is zero, what logic instruction can be used to set the ZERO flag without affecting the contents ...
0
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1answer
564 views

Programming an EPROM using 8085 kit

I need to program an EPROM/EEPROM with the code for an 8085. I do not have a programmer. I can't buy one. But I have access to an 8085 kit. Can I use it to program the EPROM/EEPROM via an interface? ...
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1answer
582 views

Identification of hardware interrupts in microprocessor 8085

I am familiar with the RIM and SIM instructions that are available in the instruction set of microprocessor 8085. And thus I can enable RST 7.5 and RST 6.5 interrupts using SIM instruction and EI ...
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1answer
22k views

Number of machine cycles in microprocessor 8085

The DCR instruction in MP 8085 has has 1 machine cycle, i.e. opcode fetch cycle. But the DCR M instruction has 3 machine cycles. What are those three machine cycles?
4
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4answers
4k views

Memory mapping in the 8085 microprocessor

In the 8085 microprocessor there is 64 kb of memory available of which some are assigned to ROM while others are assigned to RAM. My question is, why is ROM always mapped to a lower region of memory ...
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1answer
6k views

A program to add 6 bytes of data and store sum and carry in 8085 instruction set

I have a question on 8085 instruction set. A program to add 6 bytes of data stored in memory starting from 4500h. must use b register to save any carries and finally store the sum and carry at two ...
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3answers
11k views

How to set all flags in 8085?

My Microprocessor teacher of 8085 gave an assignment to set all flags ! I have written this little program to set all except Sign, Please help me out ...
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2answers
18k views

Why in HL pair, H is stored after L register

Why in 8085, during LHLD and SHLD instructions L is used first while in BC and ...
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0answers
2k views

Regarding 8085 DAD timing diagram

Can anybody tell me about DAD instruction in 8085. Is ALE high twice in first machine cycle of DAD instruction. Can anybody suggested me timing diagram of DAD and HLT instruction.(Any other link)
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2answers
187 views

Why the time of execution is never shown in any Instruction Cycle?

In case of timing diagrams of 8085, what I saw is that, always Opcode Fetch, Memory Read/Write, IO Read/Write is shown but execution is never shown. Is it because the execution time is too less ...
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1answer
2k views

Using BSR Mode of 8255 with 8085

When using the 8255 to glow an LED array using BSR mode, is it necessary to first set port c as an output port? Why? In our lab, when I had not not set port C as output and directly used BSR mode to ...
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2answers
2k views

8085 Memory address decoding with a NAND Gate

I have a problem for homework that has me stumped. Basically, what I'm given is 2 R/WMs, each 2048 bytes * 4. Connected to each of their CS pin is a NAND gate with pins A12-A15 connected from the 8085 ...
3
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4answers
10k views

what does byte 2 and byte 3 mean?

An instruction from the instruction set of intel 8085 that is SBI data (Subtract immediate with borrow) . This instruction says "The contents of the second byte of the instruction and the contents of ...
33
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4answers
115k views

What does edge triggered and level triggered mean?

I am studying 8085 microprocessor architecture and the word edge triggered and level triggered confusing me really very much. Can anyone explain me it in layman's words ? While studying the ...
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1answer
498 views

Learning about the Interrupt system of the 8085 processor

I am trying to investigate the RST5.5, RST6.5, and RST7.5 interrupts on the 8085 microprocessor. I want to find information about the to the type of interrupting signal used and the built in ...
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3answers
5k views

Reading/Writing a usb flash drive

I wish to expose a usb flash drive and read it as raw binary data, particularly read each byte & simultaneously writing it to another flash drive. Given that I am working with an 8085 ...